It is pointed out that bad breath is invisible but important from an aesthetic point of view and for leading a comfortable personal life and social life. As a result of quantitatively evaluating the effect of bad breath on oral QOL (quality of life), it is reported that the involvement of bad breath is more significant than physical appearance (Non Patent Document 1). It is further concerned that bad breath is a factor which makes it difficult to take care of aged persons in Japan where society is rapidly aging (Non Patent Document 2).
Bad breath is mainly due to three types of volatile sulfur compounds (VSCs), namely, hydrogen sulfide, methyl mercaptan, and dimethyl sulfide (Non Patent Documents 3 and 4). It is considered that VSCs are generated through the decomposition of cysteine, methionine, and the like contained in desquamated epithelial cells, leucocyte debris, food, and the like in the oral cavity by oral bacteria. It is reported, in culture tests of oral bacteria, that periodontal pathogens belonging to the genus Fusobacterium, Porphyromonas, Veillonella, Spirochaeta, and the like produce a large amount of VSC (Non Patent Document 5). In addition, it is also elucidated that Lactobacillus olis strain isolated from an oral cavity has a strong ability to produce VSCs. Since VSCs themselves have not only a significantly unpleasant odor but also toxicity to a living tissue even at a low concentration, it is also reported that VSCs are substances responsible for bad breath as well as a highly possible factor of exacerbating the pathological conditions of periodontal diseases (Non Patent Document 6). Thus, suppressing production of VSCs by oral bacteria, particularly periodontal pathogens, thereby preventing or improving bad breath is important not only for improving QOL but also for keeping a healthy oral cavity.
Recently, attempts have been made to apply probiotic technologies also to oral cavities and it is reported that, for example, Lactobacillus salivarius TI 2711 strain (Patent Document 1) is effective for bad breath, caries, periodontal diseases, oral infections, and the like.